This is taken from Tom's Hardware.
The question:
Hello all, I have a question about AMD's "8 Core" processors. Are they actually 8 core and why would anyone want an Intel Quad core processor instead?
Responses:
*No they are not real 8 core they have 4 core + 4 integral core or you can assume 4 core + 4 physical hyper threating core.Mostly one prefer intel quad core due to low power consumption,strong single threaded performance and no game uses more than 4 core.This doesnot mean that amd is not good 8 core is very usefull for heavy multitasking..etc.piledriver cpu are good at games like fx 6300, fx 8350 expect bulldozer series are not so good.
*No they are more or less quad cores, with 4 virtual cores. And for the reason behind wanting a quad core Intel... for me anyway because i game. Is that the architecture of the bulldozer is not yet really taken advantage of, and it seems to hinder performance in-game. Also if like myself you get the i7 intel you get hyperthreading which not really used in games, but it does makes the quad core more or less an 8 core itself. Depends on the person as to why you get one over they other, but Intel uses less power, and generates less heat, while the Amd is cheaper.
*They are true 8 core processors (with some shared resources) but each bulldozer core is smaller and less powerful than an Intel Sandybridge/IvyBridge core. An Ivybridge core is approximately 2.5 times as powerful on a clock for clock basis which is why Intel's quad core processors beat AMD's 8 core processors, and Intel's 6/8 core processors beat AMD's 12/16 core processors. On apps that are heavily multi threaded, the slightly higher clock speeds of AMD's 8 core Bulldozer/Piledriver processors put them "almost" on par with Intel's 4 core Sandybridge/Ivybridge processors. For applications that have little or no multithreading, they fall very far behind.
*There are 8 physical cores but 2 in a module and inside the module they share recources between 2 cores. So it's like 4 fully functional cores and 4 cores with a broken leg.
To answer your second question, Intel cpus perform more instructions per hertz, so simplified an Intel cpu at 3ghz might be faster/on par with a 4 ghz AMD cpu.
*You chose the best answer as something that is wholistically incorrect at the very core, it is so sad that this kind of information gets passed around.
AMD's modular architecture comprises of two physical x86 processors sharing pooled resources and the same front end. Unlike a native core which is a single x86 processor with its own front end and resources.
We have run the tests on this using a FX 8350, you can disable and isolate each core through all eight. Running the bench suites each isolated core performs within a 0.02% margin of error relative to all cores. This is converse to Intel where an i7 you can only isolate the 4 (or 2 depending on the SKU) physical cores, a Intel processor cannot operate on a Hyper Thread only, that is because HT doesn't use a Front End. Therein lies the difference in SMT(simultaneous multithreading) approach. AMD's CMT uses physical cores in the module, duplicating the front end to deliver around 1.8% of a true dual core peformance, the .2 loss is the penalty suffered in over taxing the front end. Intel's HT approach is around 1.1% of a dual core, HT remains only a low cost low powered attempt at SMT using virtualization of core resources.
In CPUID 1 intel core is read as 1 core 2 threads with HT enabled. Since AMD don't have that option in bios a single core is read as 1core 1 thread, 2 cores, 2 threads, if it where hyperthreaded cores in the nature of Intels as ASHISH is telling you it would register 1 core 2 threads, 8 cores 16 threads. So in short you got fed nonsense. The other funny one is a module consists of a physical and integer core, refering to the integer core as a fake core, yet as our testings and others have shown that each AMD core can be isolated and run at the exact same potential as the rest of the cores.
And lastly AMD themselves came out and clearly offered a well informed definition and description of modulation yet every man and his dog on Toms and Anandtech seems to come up with the exact same 4 cores + fake cores, which is just beyond stupefying.
The last response seem to clear it up.
